1. Field of the Invention
The invention relates to a method for the production of a three-dimensionally structured tissue paper.
2. Description of the Related Art
Tissue paper ideally displays a high absorbency and a high water absorption capacity coupled with a high tear resistance. The absorbency and water absorption capacity are defined essentially by the volume and porosity of the tissue paper. To increase the volume it was already proposed in the prior art in WO03/062528 to press the tissue paper web during production only on a zone basis in order to obtain only slightly pressed or unpressed voluminous regions and pressed regions of greater tear resistance.
During the production of tissue paper the latter is conveyed in a final drying step over the circumferential surface of a heated Yankee drying cylinder before the finished product is crêped by said cylinder. During the conveyance of the tissue paper web over the Yankee drying cylinder the tissue paper web is held by a skin.
In particular, during the production of tissue paper with voluminous areas, which are only slightly compressed during the dewatering, there is a problem in that the tissue paper has too small a dry content when brought into contact with the hot circumferential surface of the Yankee drying cylinder. This problem becomes greater on fast running machines because on such machines the dewatering times are reduced further and therefore the voluminous areas carry even more moisture.
When the tissue paper web makes contact with the heated circumferential surface of the Yankee drying cylinder, the excessively small dry content results in steam forming between the hot circumferential surface and the tissue paper web, which can lead to the web lifting off the circumferential surface.
The consequences of the tissue paper web lifting off the circumferential surface can range from runnability problems to tearing of the tissue paper web.
Furthermore, the formation of steam between the tissue paper web and the heated circumferential surface of the Yankee drying cylinder can give rise to the formation of bubbles and holes in the tissue paper web.